I am trying to get a chuck to mount on my G9972Z 11x26 lathe. After
using thread wires, I think 1 3/4 x 8 tpi is pretty damn close.

To me, the measurements look like the bolt holes more or less incline
towards the outside of the chuck .035 to .050, then we expect the poor
mounting bolt to flex back a bit to meet the adapter plate's bolt
circle. This chuck is supposed to adjust akin to a Set-Tru, yet the
mounting bolt heads are an interference fit against the outer edge of
the counterbore. It does not move about the hub when the bolts are
started. Perhaps I am too perfectionist, but this is not what I expect
of a US made chuck.

//---------------- My note to the manufacturer ------------//

Chuck and plate arrived. Chuck and plate mounting holes do not appear to
be aligned close enough to allow unimpeded operation of _adjustment_
function, adapter plate will not screw on spindle past @ three threads.

Issues: Socket head mounting boltheads are at outer edge of counterbore
in chuck face. Individual adapter plate mounting bolt hole threads are
good, all tapped holes allow you to screw in the bolts using your
fingers. When you try to mount the chuck to the adapter plate, some
bolts take a hex wrench to start. The four adjustment set screws are not
in contact with hub and are still within chuck body.

Hole pairs measured with center points, from hole center to hole center.
Hole pairs are not matched.

Chuck Chuck Adapter
(Top) (Bottom)
4.454 4.487 4.470
4.451 4.504 4.470
4.454 4.484 4.468

From the measurements, the bolt circle at the top of the chuck is @
4.501+, the bolt circle at the bottom of the chuck is 4.485+, and the
adapter bolt circle is 4.470-.

Adapter plate screws onto spindle from either side about three threads,
then stops. At first glance, the spindle threads are pretty close to 1
3/4 x 8 tpi.